This invention relates to the combination of a concrete rail bed and rails for use in connection therewith.
There have been provided in the prior art suggestions for the utilization of pre-cast concrete slabs, to be utilized as beds for the rails of a railroad. These have taken various cross-sectional shapes, and in general have been solid slabs. In some instances, generally flat constructions of the slabs have been provided, and in many instance the slabs have had neither adequate sloping shoulders for drainage, nor openings to permit rain to pass through, nor have they had a shape at the bottom thereof for providing satisfactory seating and stability on the ballast underlying the pre-cast slabs.
The provision of reinforcement for concrete has long been known, but such reinforcement has not been disclosed for concrete rail bed constructions in which a pair of pedestals are provided with slots for receiving the stem of a rail to provide the necessary strength to the concrete, in combination with the tensioned characteristics of the concrete rail bed, whether it is cast in place, or pre-cast.
Further, with regard to the providing of particular desired shapes to cast in place concrete rail beds, disclosures of construction methods have been indefinite, so that presumably only conventional shaping methods have been utilized, thereby giving results which, perhaps suitable for the shapes proposed, were not suitable for shapes of rail beds comprising a pair of spaced pedestals each for mounting a rail, and wherein the concrete used has had included in it a minimum amount of water, thereby generating a tearing and separating of the plastic cement paste and the heavier aggregate, the latter occurring when using conventional drag type slip-forms.
There have been provided, over the years, numerous shapes of rails. The most typical comprises an enlarged head, with which the flanged wheels of the railroad cars are engaged, the head being supported by a stem or web extending from beneath it, and the stem or web having at its bottom an outstanding flange. In other suggestions, the flange has been omitted, and there has thereby been provided only the head and the depending stem. Generally speaking, the rails having heads, webs or stems and flanges have been utilized by placing the lower part of the flange on a supporting structure, and then attaching the rail to the supporting structure by a clamp, spike or the like. In certain instances, there has been suggested the embedding of such rails within a concrete slab, so that the flange and stem are substantially embedded in the concrete, while the head is at the surface of the concrete slab. Such constructions have not adequately taken into consideration the various stresses imposed on rails, and the underlying supporting structure.
The stresses applied to a rail, and thus to the supporting structure are of several types. One is the downward force applied to the rail by the wheel which engages it and moves over it. Such loads are dynamic loads, due to the movement along the rail of the wheels. Thus, each part of the rail is subjected to repeated downward loads, and it is known that as the wheel moves along, the rail has an upward force directly behind the wheel.
In addition, on curves there is a lateral or generally horizontal force, caused by engagement of the flange of the wheel with the inner or gage side of the rail head. This tends to move the rail head outwardly, causing an overturning moment on the rail head, as well as causing a shear force on the rail itself, and on the supporting structure of the rail.
It is recognized, also, that the lateral forces on the rail occur even on straight portions of the railroad track, due to the swaying of the railroad cars from side to side. Consequently, lateral forces must be taken into consideration both on curves and on straight sections of the tracks, and it is also noted that this swaying exists even on curves, so that there is the possibility, which must be accounted for, of lateral forces on the inside rail of a curve.